As far as the secured card increase goes, there’s no guarantee that you will get one. I got a $100 increase on my secured card after 7 months, but a lot of people complain they never got one. You mention you received an email about getting an increase after 7 statements? Do you have a Credit Steps Program card?
Yes, it is recommended that you do not spend more than 30% of your available credit at any given time. I now tend to be more flexible with this and use a little more if I have to. The most important thing as I mentioned before is to always pay on time, and never max out your cards.